Power supplies used in welding typically convert alternating current (AC) power from a wall outlet to an output that is suitable for welding operations. The output power can be provided at a constant output current between the welding torch and a workpiece that can be controlled by directly measuring the output current of the welding torch, for example, at the contact tip or electrode of the welding torch.
Since the output current at the contact tip of the welding torch can be quite large during a welding operation, the current sensor used to directly measure the output current is typically a very expensive device such as a high current Hall Effect current sensor or a resistive shunt device. Such devices can be very expensive since they need to measure very high weld currents and need to be fairly accurate.
Further, such devices tend to be quite large such that they cannot be mounted on a printed circuit board assembly. Accordingly, additional cables are employed, thereby further adding to the cost burden for this type of architecture.
What is needed is circuitry that can control the output current of the welding torch without directly measuring the output current of the welding torch.